Structural abnormalities of the hip that result in a decreased anterior femoral head-neck ratio and/or overgrowth of the acetabular rim may result in femoroacetabular impingement (FAI). These structural abnormalities prevent the hip from having full range-of-motion. Both, loss in head neck offset and anterior overcoverage cause repetitive abnormal contact between the femoral neck and the acetabular cartilage/labrum which leads to undesirable results and require treatment.
The damage can occur to the articular cartilage (smooth white surface of the ball or socket) or the labral cartilage (soft tissue bumper of the socket). It is also believed that during the range of motion of the hip, particularly flexion and internal rotation, these structural abnormalities can initiate osteoarthritis.
Femoroacetabular impingement generally occurs as two forms, namely, Cam impingement and Pincer impingement. Cam impingement describes the femoral head and neck relationship as aspherical or not perfectly round. This loss of roundness contributes to abnormal contact between the head and socket. Pincer impingement describes the situation where the socket or acetabulum has too much coverage of the ball or femoral head. This over-coverage typically exists along the front-top rim of the socket (acetabulum) and results in the labral cartilage being “pinched” between the rim of the socket and the anterior femoral head-neck junction. The Pincer form of the impingement is typically secondary to “retroversion”, a turning back of the socket, or “profunda”, a socket that is too deep.
Combined femoral (Cam) and acetabular (Pincer) impingement are found in the majority of hips with femoroacetabular impingement. FIG. 1A shows the normal clearance of the hip; FIG. 1B shows reduced femoral head and neck offset (Cam impingement); FIG. 1C shows excessive over coverage of the femoral head by the acetabulum (Pincer impingement); FIG. 1D shows a combination of Cam and Pincer impingement.
Femoroacetabular impingement is associated with cartilage damage, labral tears, early hip arthritis, and low back pain, and while femoroacetabular impingement is common in high level athletes, it also occurs in active individuals as well as others.
With the recognition of femoroacetabular impingement as a source of cartilage damage and arthritis, new treatment options have been proposed and developed over the last decade. While initially correction was achieved through an open hip dislocation that required a trochanteric osteotomy to gain access to the acetabular rim and head neck junction, more recently these procedures are done arthroscopically.
In patients with Cam impingement, the abnormal loss of offset in the head neck junction results in cartilage delamination and arthritis. To address CAM impingement, the contour of the normal head neck junction needs to be restored. A femoral osteoplasty is a surgery to remove the bump on the femoral head neck junction and prevent cartilage delamination and the development of arthritis. This can be done open or arthroscopically. During arthroscopic or open femoral osteoplasty, the excessive bone is removed using a chisel (open) or a burr (arthroscopically).
In the case of Pincer type impingement and in the case of a retroverted acetabulum, it can become necessary to perform rim trimming to reduce the acetabular overgrowth. In order to do this open or arthroscopically, the labrum needs to be detached from the rim and the bone needs to be removed using a chisel or arthroscopically using a burr.
Recent studies have shown that patients with labral repair have a better outcome than patients with a resected labrum. In a recent study, showed that 28% of the patients had an excellent result after removal of the labrum but 80% of the patients had an excellent result when the labrum was reattached.
In cases of cartilage delamination secondary to Cam impingement or in cases of traumatic cartilage lesions that exposes the subchondral bone, microfracture is often the only treatment option to restore cartilage in the hip. Microfracture is a technique that utilizes pick or awl to penetrate the subchondral bone and allow blood flow into the cartilage defect and form a “super clot”. This clot contains stem cells that under cyclic loading during the postoperative rehabilitation differentiate into chondrocytes and start forming fiber or hyaline like repair cartilage. Microfracture repair of articular cartilage lesions in the knee results in significant functional improvement at a minimum follow-up of two years. When comparing cartilage transplantation and microfracture, both methods have acceptable short-term clinical results. Studies have shown that there is no significant difference in macroscopic or histological results between the two treatments techniques. Microfracture is gaining increasing acceptance for the treatment of patients with full thickness cartilage lesions in the hip. However, conventional microfracture picks suffer from the disadvantages described herein.
Despite the recent improvements in treating femoroacetabular impingement, there is a need to provide improved instruments and techniques that can be used to treat femoroacetabular impingement of both types.